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5163590 
Journal Article 
L-Phenylalanine inhibition of human alkaline phosphatases with p-nitrophenyl phosphate as substrate 
Komoda, T; Hokari, S; Sonoda, M; Sakagishi, Y; Tamura, T 
1982 
Yes 
Clinical Chemistry
ISSN: 0009-9147
EISSN: 1530-8561 
28 
12 
2426-2428 
English 
7139925 
With p-nitrophenyl phosphate as the substrate, there reportedly is no organ-specific inhibition of alkaline phosphatase (EC 3.1.3.1) activity by L-phenylalanine. However, we found that at pH 10.0, with p-nitrophenyl phosphate as the substrate, L-phenylalanine obviously inhibits the alkaline phosphatase isoenzyme from human placenta, whereas there is little if any inhibition of the isoenzyme from human intestine. Because of the differing effects of substrates (p-nitrophenyl phosphate and phenyl phosphate) and their enzymic products (p-nitrophenol and phenol) for L-phenylalanine action on the placental alkaline phosphatase isoenzyme, we suggest that the isoenzyme--inhibitor--substrate complex and the effect of released phosphate on L-phenylalanine inhibition of the isoenzyme activity differ from each other. 
Adult; Alkaline Phosphatase/antagonists & inhibitors; Enzyme Activation/drug effects; Hydrogen-Ion Concentration; In Vitro Techniques; Intestinal Mucosa/enzymology; Nitrophenols/metabolism; Organophosphates; Organophosphorus Compounds/metabolism; Phenylalanine/pharmacology; Placenta/enzymology